Historically, flexible bulk containers have been used for receiving, storing, transporting and discharging flowable materials of all types. The containers are typically constructed in a square or vertically rectangular shape with lift straps attached to each of the uppermost corners of the square or rectangle.
Four panels are stitched together to form a perimeter wall in turn stitched to upper and lower panels to form the enclosed container. The panels used to form the perimeter wall are stitched together such that the seams connecting the panels are located in the corners of the container. The lift straps are typically stitched or otherwise attached to the uppermost corners of the container and adjacent to the seams connecting the panels to form the perimeter wall. Thus, through placement of the panel seams and the lift straps on the four corners, when filled, a substantial load is placed on the corners, thereby stressing the seam and threatening the integrity of the container.
In some instances, the ends of the lift straps are attached to the side panels at points away from the corner seams and extend up and over the corners of the top panel to form a loop. To reinforce the lift straps attached in such manner, a reinforced webbing material extends vertically down the side of the container at the location of attachment of the ends of the lift straps. Thus, when the container is filled, lifting of the straps diverts some of the load stress away from the seamed corners, but concentrates more of the load on the spread apart ends of the lift strap.
Although square in shape when empty, upon filling, flexible containers assume a more rounded shape. Bridge panels have historically been attached to the interior of the containers to achieve a less rounded configuration when the containers are filled. The bridge panels are typically the same height but smaller in width than the side panels forming the perimeter wall. Opposed edges of the bridge panel are attached vertically to adjacent side panels with the seam connecting the adjacent side panels located between the vertical attachment points of the bridge panel to thereby define a triangular shaped area between the bridge panel and the corner seam connecting the adjacent side panels to which the bridge panel is attached. Such configuration has historically caused construction problems requiring the handling of multiple panels while attaching the interior bridge panels.
The present invention overcomes the foregoing and other problems heretofore experienced in construction and use of flexible bulk containers. With reference to a first embodiment of the invention, four side panels are seamed together to form a perimeter wall in turn attached to a bottom panel and, in some cases, a top panel in such a manner that the corners of the bottom and top panels are seamed to the perimeter wall at points equidistant from the seams connecting adjacent side panels forming the perimeter wall. In other words, the seams connecting the side panels fall not at the corners, but at locations along the perimeter wall at midpoints between the corners of the top and bottom panels.
Lift straps are attached to the perimeter wall of the container with the opposed ends of the strap being attached beginning at adjacent seams connecting the panels and extending diagonally upwardly and away from the seam to the point where the perimeter wall is attached to the top panel. A center portion of the strap extends upwardly from the attachment points to the perimeter wall and diagonally over the corner of the top panel to form a loop above the corner. Thus, the straps are attached to the container along the sides as opposed to the corners of the container. Each strap is attached to its individual associated panel prior to seaming the panels to one another to simplify construction of the container.
By offsetting the side seams and attaching the straps to extend from the seams and loop over the corners, the load is more evenly distributed over the entire container with the added strength of a continuous piece of the container material extending around each corner. Such construction also allows for easier attachment of bridge panels. The panels are still attached to bridge the corners of the container, but because each corner is formed at the midpoint of a single panel, each bridge may be separately attached to a single panel prior to attaching the side panels together to form the perimeter wall. Therefore, instead of having to handle four panels at once to attach a single bridge panel, only two panels at a time are handled.
In a second embodiment of the invention, two side panels are attached along the bottom and both side edges to a single long panel to form the perimeter and bottom walls of a container. A top panel is then attached to the upper edge of the perimeter wall such that the corners of the top panel are attached at points along the perimeter wall equidistant from adjacent seams connecting the long panel to the side panels. Thus, the construction of the top portion of the container is the same as the construction of the top portion of the first embodiment container. Substitution of the single long panel for the bottom and two side panels of the container results in the top corners of the containers being offset from the bottom corners of the container. The lift straps may be attached in the same manner as in the first embodiment of the invention. As with the first embodiment of the invention, the positioning of the corners of the top panel away from the seams connecting the side panels results in a more even distribution of the load throughout the container, thereby reducing the threat of failure of a filled container.